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Utility of an Instantaneous Moisture Meter for Duff Moisture Prediction in Long-Unburned Longleaf Pine Forests

Engber, Eamon A., Varner, J. Morgan, Dugaw, Christopher J., Quinn-Davidson, Lenya N., Hiers, J. Kevin
Southern journal of applied forestry 2013 v.37 no.1 pp. 13-17
climate, coniferous forests, drought, fires, forest litter, fuels (fire ecology), managers, mortality, overstory, prediction, prescribed burning, soil heating, tree mortality, trees, water content
Duff fires have been implicated in overstory mortality and soil heating in long-unburned pine forests. In the South's punctuated climate, duff moisture can change rapidly, falling below moisture thresholds that protect trees or increasing after brief downpours. To date, managers lack an instantaneous measure of duff moisture, a hurdle to the implementation of prescribed burns. Here, we evaluate a low-cost tool, the Campbell Scientific Duff Moisture Meter (DMM) 600 (Campbell Scientific, Logan, UT), to estimate duff moisture content in the field. Comparisons of the DMM 600 outputs with paired oven-dried duff fuel samples revealed statistically significant differences, with DMM 600 moisture output explaining 54% of the variation in oven-dried moisture content. Comparisons with previously published data indicate that large variations in duff moisture calculations may predict a broad range of observed duff consumption and overstory tree mortality levels, limiting its applicability for some management objectives. DMM 600 outputs were only weakly correlated with Keetch-Byram drought index (R2 = 0.30). In addition, we encountered some operational difficulties in prolonged field use. In spite of a few shortcomings, the DMM 600 provides a low-cost tool to assist in prescribed fires where deep forest floor fuels exist.